Heretofore, there has been known an automatic faucet for automatically starting and stopping spouting water by using a radio wave sensor (see, for example, the following Patent Document 1). Such an automatic faucet comprises a photoelectric sensor installed inside a distal end of a conduit pipe. When a user inserts his/her hand within a sensing range of the photoelectric sensor, the photoelectric sensor senses the presence of the hand, and, in response to the sensing, spouting of water from a spout port is automatically started. Then, when the user pulls out the hand from the sensing range, the photoelectric sensor ceases to sense the presence of the hand, and thereby the spouting of water from the spout port is automatically stopped.
Meanwhile, in the automatic faucet, during use, a user can move his/her hand toward the spout port from various directions. On the other hand, the photoelectric sensor has strong or narrow directivity. Thus, in order to reliably sense the user's hand being inserted from various directions by using the photoelectric sensor, it is necessary to install the sensing range of the photoelectric sensor at a position adjacent to the spout port where the user's hand is certainly placed. This means that the user's hand can be sensed by the photoelectric sensor only after it reaches the spout port. Thus, the automatic faucet using the photoelectric sensor has difficulty in obtaining enhanced response.
There has also been known an automatic faucet using a radio wave sensor (microwave sensor) having a broad sensing range, instead of the photoelectric sensor (see, for example, the Patent Document 2). In an automatic faucet described in the Patent Document 2, a radio wave sensor is installed on the side of a sink, and a direction of a radio wave beam to be emitted from the radio wave sensor is set to be oriented upwardly.
As compared to the photoelectric sensor, the radio wave sensor has wider directivity and a broader sensing range. Thus, the automatic faucet using the radio wave sensor is capable of, even if a user moves his/her hand toward a spout port from various directions, sensing the user's hand before it reaches the spout port, thereby obtaining enhanced response.
In the automatic faucet using the photoelectric sensor, in addition to the above problem that it is not easy to obtain enhanced response during start of water spouting, the necessity to install the photoelectric sensor at a position adjacent to the spout port due to its characteristics gives rise to another problem of deterioration in design flexibility. That is, the photoelectric sensor and associated components such as wirings and electric components have to be installed within the conduit pipe at positions adjacent to the spout port, which imposes restrictions on design flexibility.
On the other hand, the automatic faucet having the radio wave sensor installed on the sink side can enhance design flexibility. However, it is not easy to achieve adequate response. That is, due to the layout where the radio wave sensor is installed on the sink side, if it is attempted to increase a radio field intensity in a vicinity of the spout port, the radio field intensity will be increased not only in the vicinity of the spout port but also all around the faucet, resulting in an excessively broad sensing range. Thus, the automatic faucet having the radio wave sensor installed on the sink side has a problem that erroneous water spouting is more likely to occur in response to a water removing motion just after completion of hand washing, and a hand-lathering motion during hand washing.
Therefore, the applicant (inventors) of this application proposed an automatic faucet in which a water pipe and waveguide are provided side-by-side within a conduit pipe, and a radio wave is guided from a radio wave sensor to a spout region via the waveguide (see the Patent Document 3). This automatic faucet can set a sensing range around a spout port. Thus, it is considered that response during start and stop of water spouting can be enhanced.